The Physiological and Psychological Class of Problem Addressed
Before addressing specific background art, a description of the mechanism and consequence of involuntary passageway closure in living organisms is provided.
The most common and most serious dysfunctions caused by the involuntary closure of a passageway in humans occur in a debilitating and life-threatening mode in the disease known as "sleep apnea" and as an inconvenience (in aesthetic and/or psychological senses in various degrees) for those afflicted with severe snoring. There are other human and animal afflictions also connected with the involuntary closure of vital passageways to which techniques used to alleviate or cure apnea may also pertain.
In the case of sleep apnea, what occurs is an involuntary closure of a portion of the air passageway, or windpipe (also called the "airway"), that connects the mouth to the lungs and digestive system. The upper portion of the airway (the "upper airway") consists of two passageways, the nasal airway and the oral airway. Portions of the upper airway just back of the tongue are known as the soft palate, the hypopharynx, etc. Below the tongue, these two passageways merge to become a single passageway. Portions of this lower single passageway are known as the throat, the gullet, the trachea, the pharynx, the larnyx, the thorax, the esophagus, etc. Closure commonly occurs when the patient sleeps, because then his or her muscles are in a condition of minimum tenseness, indeed in the condition of relaxation associated with sleep. In those people prone to sleep apnea, there is a tendency for a portion of the inner walls of the air passage, generally in the region just back of the tongue, to become so limp and relaxed as to have a tendency to "flap shut". At that instant, the air passage is blocked, breathing stops, air movement to the lungs ceases, and the patient begins to choke. He or she awakes in a state of panic, gasping for breath, which resumes as the throat tissues tense and tighten, thus "unflapping" the closure and thus unblocking the air passage.
The patient then resumes sleeping, but another apneic attack generally follows. For those severely afflicted, there may be as many as eight episodes per hour. When these conditions persist, patients are at best constantly drowsy during the day due to constant waking up during the night, or at worst, develop heart conditions which lead to heart attacks.
There are two locations in the upper airway where apneic episodes may occur. The rates of incidence in both locations are about equal, so that they are equally important. The first location is at the soft palate at the rear of the tongue, where it makes a boundary with the nasal airway. This may flap shut against the posterior pharyngeal region which makes up the rear wall of the throat. The second location is lower down at protruding tissue, known as the hypopharynx, in the region where the nasal and oral airways merge. It, too, can flap shut against the posterior pharyngeal tissue. The hypopharynx is integral with the subglottal tissue which moves with it as it flaps shut.
People most prone to sleep apnea are generally overweight and/or with receding jaws. Some animals, especially the bulldog and the Pekingese, are prone to sleep apnea. This accounts for the fact that bulldogs are characterized as "sleepy".
Snoring is actually a mild form of sleep apnea in that total closure and blockage of air movement does not occur, but partial blockage does. Acoustical vibrations are then set up, not dissimilar from those generated in the mouthpieces of brass musical instruments, like the trumpet or trombone. These resonate and are amplified and fortified in the throat and nose chamber and emerge as the unpleasant sounds we know as snoring.
Some authoritative references on the subject of sleep apnea are Guilleminault, C., "Diagnosis, Pathogenesis, and Treatment of the Sleep Apnea Syndromes", Springer-Verlag, Berlin 1984, Block A. J., et al., "Factors Influencing Upper Airway Closure", CHEST Vol. 86, No. 1, July 1984, p. 114, and Sullivan, C. E., et al., "Obstructive Sleep Apnea", Clinics in Chest Medicine, Vol. 6, No. 4, Dec. 1985, p. 633.
Various procedures and devices have been developed for the mitigation of the effects of apnea. These are described below: